The human spine includes individual vertebras that are connected to each other. Under normal circumstances the structures that make up the spine function to protect the neural structures and to allow us to stand erect, bear axial loads, and be flexible for bending and rotation. However, disorders of the spine occur when one or more of these spine structures are abnormal. In these pathologic circumstances, surgery may be tried to restore the spine to normal, achieve stability, protect the neural structures, or to relief the patient of discomfort. The goal of spine surgery for a multitude of spinal disorders especially those causing compression of the neural structures is often decompression of the neural elements and/or fusion of adjacent vertebral segments. Fusion works well because it stops pain due to movement at the facet joints or intervertebral discs, holds the spine in place after correcting deformity, and prevents instability and or deformity of the spine after spine procedures such as discectomies, laminectomies or corpectomies. Discectomy and fusion are commonly performed in the cervical spine but there is increasing application in the thoracic and lumbar spine, as well.
Several spinal fixation systems exist for stabilizing the spine so that bony fusion is achieved. The majority of these fixation systems utilize fixation elements such as rods wires or plates that attach to screws threaded into the vertebral bodies, facets or the pedicles. In addition to stabilization of the vertebral elements with fixation elements, there is a need to maintain the decompression of the intervertebral discs where discectomies or microdiscectomies have been performed. Some of theses decompression methods include inserting an implant in the intervertebral space between two adjacent vertebras in order to maintain the desired axial distance from the superior and inferior vertebral wall. The intervertebral implant is usually made of a biocompatible material in the shape of a hollow block. The intervertebral implant may be inserted from the anterior, posterior, from a transforaminal approach, or medial/lateral approach. In other decompression methods, bone growth material such as bone graft, harvested bone, or dematerialized bone matrix are injected, inserted, or impacted into the disc space. This material fills the space remaining from the discectomy procedure and acts as a catalyst for bone growth and bone fusion within the disc space.
The use of stabilization rods in combination with the insertion of an intervertebral implant is effective in treating several spinal disorders. However, the operating procedure for attaching the rods and inserting the intervertebral implant is usually long. Accordingly, it is desirable to provide an intervertebral implant that offers both stabilization and decompression of adjacent vertebras.